The invention is in the field of mechanical engineering, in particular micromechanics, and specifically relates to blood pumps.
U.S. provisional application Ser. No. 61/364,559, U.S. provisional application Ser. No. 61/364,595, and U.S. provisional application Ser. No. 61/364,578 are hereby incorporated by reference.
The use of the invention is in particular in the medical field where corresponding blood pumps have already become known in different designs for different purposes. Such pumps can be used invasively and can for this purpose be introduced via a blood vessel into the body of a patient and can be operated there. Such pumps can be used particularly advantageously, for example, in a cardiac chamber, especially in a left ventricle, to assist the heart. Such a pump is for this purpose pushed in via a femoral artery by means of a hollow catheter and is introduced up to and into the left ventricle of a patient's heart. The blood pump there sucks in blood and expels it again in the aorta. In this manner, the heart's function can be replaced at least in part or can be assisted in order, for example, to relieve the heart in surgical procedures in this manner or to improve the conditions for a recovery of the patient's heart.
Such a pump has a drive which can, for example, be disposed outside the patient's body and the drive motion is transferred from said drive through the hollow catheter to the rotor by means of a rotatable shaft. However, the operation of microturbines in the proximity of the blood pump is also known for its drive.
A problem in the efficiency of such pumps is represented by the small dimensions which are advantageous for the transport within the patient's body. Such a pump or the rotor is usually radially compressible for the transport in order then to be expanded for the actual operation.
Various constructions have become known which allow a change of the rotor between a compressed state and an expanded state. Constructions are, for example, known having support struts made from memory alloys which change their shape in dependence on the environmental temperature. The support structures can then be spanned by a membrane to form the impeller blades of a rotor.
Single-part rotors with hubs are also known to which impeller blades are fastened in one piece which can be folded onto the hub and spread apart from it due to their balanced elastic properties. The compression of the impeller blades often takes place by the housing which surrounds the rotor and can be enlarged for the expansion. The erection of the impeller blades can take place, for example, by the rotation of the rotor in operation in that the impeller blades are erected by the arising fluid counter-pressure on the rotation.
A problem in the construction of such blood pumps is, for example, that the demands on the material properties of the material from which the rotor or especially the impeller blades are made are very high. The impeller blades have to be deformed a great deal in locally bounded regions for the complete folding onto the hub, and it is also desirable that the compression forces required for the compression remain small to be able to compress the rotor without any great effort and without any excessive wear. Composite materials have been proposed for this purpose for manufacturing the impeller blades.
On the one hand, they provide an impeller blade body made from a relatively elastic material and on the other hand additional struts which can be integrated into an impeller blade body or which can be placed onto it and which stabilize and support the impeller blade at least in the expanded state.
Various proposals have already become known for a sensible expansion of both the rotor and of the housing surrounding it, such as, for example, the proposal also to expand the housing by the expansion of the rotor or to expand the housing independently of the rotor and thereby to allow the elastic forces acting in the rotor to work which at least partly expand the impeller blades automatically.
Corresponding constructions have become known, for example, from WO 03/103745 and WO 94/05347. It is also proposed there, for example, to apply longitudinal forces to the housing in order to compress it axially, for example, as part of a puling movement, and thus to expand it radially.